Foundry workers moving a crucible of molten bronze used in the process for making bronze sculpture.

LOST- WAX CASTING PROCESS

Geoffrey uses a method of casting for his sculptures called the "Lost-Wax Process", a translation of the French term "cire perdue". This complicated method creates a metal duplicate from an original sculpture. This lost-wax process is said to date back to the 3rd millennium BC. It was widely used across Europe until the 18th century. Working this way is slow and tedious, but is arguably the best method to obtain high-quality bronze sculptures.

​It all begins when Geoffrey finishes the original clay sculpture and sends it to the foundry to be transformed through the lost-wax process.

Read more about it and watch the video below.

picture of a Rubber Mold used for the Lost wax process of making bronze sculpture.

THE MOLD

The mold-making begins with a liquid rubber mixture being applied to the original sculpture. This mixture is hand applied by brush to make sure it gets into even the tiniest crevices, picking up the fingerprints and texture marks left behind by the sculptor. The liquid rubber is allowed to dry in between layers until it forms a thick soft layer creating an inner mold.  A hard outer layer or the "mother mold" is created using plaster. The plaster is applied to the outside of the rubber mold by hand stopping to allow layers to dry until the plaster mold is complete. Once the rubber mold and plaster mold are finished they are an exact negative of the original sculpture. Depending on the size and other factors of the piece, the original clay sculpture might be cut into sections to be molded resulting in multiple molds for a single sculpture.

A wax Octopus model used in the Lost Wax process to create a bronze sculpture

THE WAX MODEL

The mold is then used to create the wax model. Since most sculptures are hollow the melted wax is applied in layers. The wax is poured into the mold and swished around to obtain an even layer inside the mold. The excess wax is poured out and the layer is allowed to cool before the next batch of melted wax is poured into the mold and the process is repeated until the desired thickness is achieved. When complete and cooled the wax model is removed from the mold. The mold can be stored for later use.

Wax Models used to make bronze sculptures at the foundry.

CHASING AND SPRUING

Now that a wax model has been created it goes through a process called chasing. This is where all the bubbles, mold lines, and any imperfections are filled and smoothed with heat and wax making the wax model as close to the original sculpture as possible.

When the chasing is complete the wax channels called "sprues" or "gates" made of a tree-like structure formed of wax which is attached inside the wax model next a "cup" is placed on top and attached to the structure of sprues. These channels will act as funnels for the liquid bronze, allow air to escape, and eventually enable the wax to melt out of the shell.

White Ceramic Shell for sculptures to be used at the foundry to create bronze sculpture

CERAMIC SHELL
Once the wax model is complete it is dipped in a liquid ceramic mixture then covered in fine sand. When this first coat is dried these steps are completed until the desired thickness is obtained. Now there is a ceramic mold with the wax model still inside.

Ceramic Shells in a burn out oven at the foundry used to make sculptures.

LOST WAX
After the ceramic shell is finished it is placed into a furnace to cure. During this step, the wax model melted out, and we are left with the ceramic shell which includes the sprues and cup.
This is where the name "lost wax" originated. Since each sculpture has to have a wax model and each time a bronze is poured the wax is lost when melted away.

Molten bronze being poured in a ceramic shell to create a bronze sculpture

The BRONZE POUR
The empty ceramic shell is now filled with molten bronze. The bronze around, 2100 degrees Fahrenheit, is poured into the cup and flows through the "sprues" into the negative space.

Shows the white ceramic mold after being broken off, the raw bronze is exposed.

THE BRONZE REVEALED
After the bronze has cooled the ceramic shell is broken away revealing the raw bronze sculpture.

Raw Bronze Conch Sculpture at Foundry

CLEANING AND WELDING
Following the removal of the ceramic shell, we are left with rough bronze. At this stage, if the sculpture was cast in multiple pieces the separate pieces will be welded together.  Now it will be sandblasted, cleaned and chased to bring it back to a copy of the original clay sculpture. This is done with such care and precision you will not be able to tell that it was more than one piece.
 

Chemicals being applied with a brush to a Pelican sculpture being during the patina process

THE PATINA
The last step before the sculpture is ready for its new home is the patina process. This is where the color is added. By heating the bronze and applying different combinations of chemicals, acids, and pigments many different color variations can be achieved. Once the patina is finished a layer of wax is applied to the sculpture for protection.